BackgroundIn patients with complex regional pain syndrome (CRPS), the temperature of the affected side often differs from that of the contralateral side. In the acute phase, the affected side is usually warmer than the contralateral side, the so-called warm' CRPS. This thermal asymmetry can develop into a colder affected side, the so-called cold' CRPS. In contrast to cold CRPS, in warm CRPS, inflammation is generally assumed to be present. However, there are reports of cold CRPS patients, successfully treated with vasodilatation therapy, who subsequently displayed warm CRPS. It seems that inflammation could be hidden' behind vasomotor disturbance. This study was designed to test this hypothesis. MethodsA retrospective analysis was made of patients in our CRPS database. We defined three types of CRPS: cold CRPS, neither cold nor warm (intermediate) CRPS, and warm CRPS. Of these patients, the difference between the level of the pro-inflammatory cytokines interleukin (IL)-6 ( IL-6) and tumor necrosis factor (TNF)- ( TNF-) in the affected extremity and that in the contralateral extremity was determined. ResultsThe bilateral difference of the level of these cytokines did not differ among patients with cold CRPS, intermediate CRPS, or those with warm CRPS. ConclusionInflammation may be involved in cold CRPS.